Research and simulation on constant switching frequency of direct torque control(DTC)

Direct torque control (DTC) used in AC-drive locomotive control system, which has been developed in the recent decade, is a control strategies with high dynamic and static performance, and it directly generate the inverter gate control signal by judging the output of the stator flux, torque hysteresis comparator and the position information of the stator flux that cause the switching frequency unfixed. While now the highest switching frequency of the IGBT used in AC-drive locmotive is 1000 HZ. If the switching frequency could be fixed, the precious switching resources will be used fully and the cost of IGBT will be reduced greatly. A method of fixing the switching frequency is presented in this paper, and the MatlabSimulink model have been made to verify the accuracy of it.